Article ID: 2623817 - View products that this article applies to.
Consider the following scenario:
This issue occurs because the Lync 2010 client receives a 488 not acceptable here response, and then the client does not rejoin the focus conferencing component.
To resolve this issue, install the following cumulative update:
(http://support.microsoft.com/kb/2514982 / )Description of the cumulative update for Lync 2010: November 2011
Note after the update is applied, Lync 2010 rejoins the focus conferencing component when the client receives the 488 not acceptable here response.